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What is the test for the APOE genotype that predicts Alzheimers?April 30, 2010 3:58 PM Subscribe

My mother has alzheimers. I want to have the "APOE4" test done on myself to find out my likelihood of getting alzheimers. My doctor doesn't know much about this, and I am having trouble figuring out what test to ask for.

My mother had genetic testing and she is Apolipoprotein E Genotype: 3 and 4. I'd like to get the same test for myself but we have different doctors and my doctor doesn't know these test well. She sees these options on a list of tests she can request:

The APOE genotype $104.55APOE4(lots a numbers) $32.50

My doctor is not familiar with these test so I am not sure which of these, if any, corresponds to the test my mother got, especially since her test cost $400.

How do I specify the test I need. The point, I believe, is to figure out whether or not I am destined to get Alzheimers.

Any additional comments on the meaning of these tests and their value appreciated.

See a medical geneticist... they can order the test and provide the counseling you would need for this.posted by Brennus at 4:29 PM on April 30, 2010

The point, in my understanding, is to determine if you carry the gene. If you carry 2 alleles of the gene, it increases your risk, but does not mean that you will absolutely get Alzheimer's. Whether or not the gene is expressed is a matter of time and can be influenced by a number of factors. I agree that you should see a geneticist, but hope that the little bit of info I gave you might be helpful.posted by bolognius maximus at 4:31 PM on April 30, 2010

Your mother has a normal allele (E3) and a dysfunctional allele (E4).

The protein ApoE is polymorphic with three major isoforms, ApoE2, ApoE3, ApoE4, which translate into three alleles of the gene:Normal: ApoE-ε3Dysfunctional: ApoE-ε2 and ApoE-ε4

E3 is considered the "neutral" Apo E genotype. E4 has been implicated in atherosclerosis and Alzheimer's disease, impaired cognitive function, and reduced neurite outgrowth.

Worst case would be if you received the E4 from your mother and a E4 gene from your father. Even if this is the case, it does not mean that you are going to get Alzheimer, but that your risk is increased 10 to 30 times the general population. From Wikipedia: There is also evidence that the ApoE2 allele may serve a protective role. Thus, the genotype most at risk for Alzheimer's disease and at earlier age is ApoE 4,4. The ApoE 3,4 genotype is at increased risk, though not to the degree that those homozygous for ApoE 4 are. The genotype ApoE 3,3 is considered at normal risk for Alzheimer's disease. The genotype ApoE 2,3 is considered at less risk for Alzheimer's disease. Interestingly, people with both a copy of the 2 allele and the 4 allele, ApoE 2,4, are at normal risk similar to the ApoE 3,3 genotype.

As you can see, things are not that simple and even if you are E3E4, just like your mother, it does not mean that you have a 100% chance to get Alzheimer. Here is a link to Genetests, with a directory of places (not many) that do the test. The reason that the test is not offered by a lot of labs is that the gene was patented: 12 years or so ago my lab used to offer the test, but we were told to "cease and desist".posted by francesca too at 4:39 PM on April 30, 2010 [4 favorites]

These tests can have significant implications for both you physical and mental health. You should not take this lightly. Seek out a genetic counsellor and take the timeto understand the possible outcomes of find out what your ApoE varient is.posted by SueDenim at 7:23 PM on April 30, 2010 [1 favorite]

seconding (or thirding,fourthing) that your next consultation should be with a geneticist that can explain the test and its results to you and empower you to make the choice about whether to have it, why you want to have it and what will happen once you have the results. this is what your doctor should have recommended as well.

you specifically asked what the value of these tests is, and as they are designed, they are meant to predict the *probability* of all the individuals diagnosed with a given genotype to get or not get the disease. they are not guaranteed to predict the certainty that one individual (i.e. you) to get or not get the disease based on the genotype that you possess. the results should come with that disclaimer.posted by Tandem Affinity at 8:45 PM on April 30, 2010

Labtestsonline is the most comprehensive source for clinical laboratory testing. Their entry on ApoE genetic testing is worth reading as well as wikipedia's. The set of numbers in the test name were probably rs429358-rs7412 which correspond to the specific single nucleotide polymorphisms or SNPs which are tested.